The heliostat is an important device frequently involved in the utilization of solar energy, and it is mainly used in lighting or thermal power generation with solar energy.
For instance, in thermal power generation with a tower using solar energy, the solar heat radiation is reflected by a number of heliostats to a solar receiver mounted on top of a high tower, to heat the medium to produce superheated steam, or to directly heat water in the heat collector to produce superheated steam, which then drives the turbo-generator set to generate electricity, thus converting solar energy into electrical energy. To enable the solar radiation to be reflected onto the fixed receiver by reflectors at all times during the day, a tracking mechanism must be provided for the reflectors. To control the tracking mechanism, two forms are mainly adopted nowadays, namely, programmed control and control by sensors. With programmed control, the movement of the dual-shaft tracking mechanism is controlled according to the calculated sun movement route. Programmed control has the shortcoming of accumulated error and high cost. With control by sensors, the movement of the tracking mechanism is controlled according to the incident sun radiation direction measured by the sensors. Control by sensors has the shortcomings that: (a) it cannot control the reflected light directly, (b) as there is mechanical error in precision that cannot be overcome, it is difficult to ensure accurate tracking and positioning by solely relying on the tracking sensors mounted on the tracking mechanism, and (c) it cannot realize stable and reliable control.